This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project has as its principal goal the characterization of the expression and action of a novel isoform of the Her-2 protooncogene. This isoform, termed herstatin, results from intron retention and the synthesis of a truncated version of Her-2 containing a unique intron-encoded C terminus. The studies supported by this award include assessment of expression and inhibition of growth of prostate and breast cancer cell lines in vitro using transwell co-culture as well as investigation of the activity of C-terminal fragments of the full-length protein. We have most recently investigated the secretion of herstatin from multiple cell lines using both plasmid vector and lentivirus approaches and have employed heterologous signal sequences to enhance secretion.